improve syncing and storing

back/db/structureV2.sql

@@ -126,6 +126,7 @@ CREATE TABLE app_room (
   notSeen         INT NOT NULL DEFAULT 0,
   lastUpdate      TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP(),
   PRIMARY KEY (room_id),
+  UNIQUE KEY (owner_id, message_id, isGroup),
   FOREIGN KEY (owner_id) REFERENCES address(address_id),
   FOREIGN KEY (message_id) REFERENCES message(message_id)
 );